This is a competing continuation application to extend research begun in 2001 on NIDA's Clinical Trials Network and its role in the diffusion of evidence-based practices (EBPs). The continuing project would examine the multi-faceted impact of the CTN on substance abuse treatment using a longitudinal design that integrates multiple methods to fully document the activities of the Network. Specifically, we propose to study the processes related to diffusion, adoption, implementation, and re-invention of techniques examined in CTN research protocols among the participating community-based treatment providers (CTPs). Using data already in hand, we will also examine these same processes in representative samples of treatment facilities outside the Network. This longitudinal design offers the opportunity to track the diffusion, adoption, and potential reinvention of interventions that have been empirically supported in CTN trials. Focal practices will include those with findings now available for public dissemination, and new CTN findings that will become available over the next several years. Pharmacotherapies, psychosocial counseling approaches, and combined medication/counseling techniques are included in the CTN portfolio. Comparative data available from programs outside the CTN provide a basis for assessing the broader impact of the CTN on EBP diffusion, as well as understanding the impact of clinical trial exposure on organizational and staff attitudes toward the adoption of innovative treatment practices. The adoption of EBPs is critical to enhancing the quality of drug addiction treatment via improved client retention and outcomes;as a result, this health services research project has direct implications for public health and public policy.